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Opinions about problem with e magnetos

Robert Sailor

Well Known Member
I recently purchased a very nice RV6A with an IO-320 and Hartzel prop. It has a single Bendix Magneto and an electronic magneto.
When I test flew it I had a mag drop on the Bendix of around 150 rpm and about 10-15 rpm drop on the electronic magneto and the engine ran very smooth.
The lower plugs are fine wire plugs and the upper plugs are a good quality automotive plugs
I decided to put new plugs in the upper ones rather than clean and gap the old plugs.
Now the electronic magneto is dropping around 150 rpm, almost the same as the Bendix and I'm left scratching my head as to what may have caused this. The only thing done was to install new plugs. Anyone have any ideas as to what may have happened. Engine is still running well with both mags on. Robert
 
I recently purchased a very nice RV6A with an IO-320 and Hartzel prop. It has a single Bendix Magneto and an electronic magneto.
When I test flew it I had a mag drop on the Bendix of around 150 rpm and about 10-15 rpm drop on the electronic magneto and the engine ran very smooth.
The lower plugs are fine wire plugs and the upper plugs are a good quality automotive plugs
I decided to put new plugs in the upper ones rather than clean and gap the old plugs.
Now the electronic magneto is dropping around 150 rpm, almost the same as the Bendix and I'm left scratching my head as to what may have caused this. The only thing done was to install new plugs. Anyone have any ideas as to what may have happened. Engine is still running well with both mags on. Robert

Is the electronic magneto and E-Mag brand unit or something else? I would confirm that the plugs have the proper gap. I assumed you replaced with the exact same brand and part number (probably NGK-BR8ES or similar).
 
Is the electronic magneto and E-Mag brand unit or something else? I would confirm that the plugs have the proper gap. I assumed you replaced with the exact same brand and part number (probably NGK-BR8ES or similar).

I have to double check the exact brand of e mag and yes I used exactly the same plugs but I didn't regap them.
 
The gap on the BR8ES is usually pretty tight out of the box and needs to be opened up. Don't have the spec handy but I think it's .032 for Emag.
 
The gap on the BR8ES is usually pretty tight out of the box and needs to be opened up. Don't have the spec handy but I think it's .032 for Emag.

Is there a way to confirm the gap at .032? It's manufactured by E Mag. Would a smaller gap result in a larger mag drop? Thanks, Robert
 
The plugs I used were NKG Iridium plugs, after a bit of homework I see they come with a .044 gap but the E mag specs a gap between .030-.035. I'll pull them and regap the plugs but it appears the stock gap is quite a bit larger than the one spec'd for the E mag.
 
So I removed the plugs and the factory gaps were smaller, not larger than .032. I regapped the plugs and reinstalled with similar results, still a much larger mag drop than I had before changing plugs??? Runs smooth enough at cruise power, not so great at idle at times.
 
Try pulling the plug wires off the back of the Emag and checking for corrosion - clean if found and replace (do one at a time to make sure they get back on the same spots). I’ve had a little corrosion that caused rough running before. Not saying that’s your problem - but its something to check. There is a spec resistance per foot in teh Emag manual for the plug wires, and you can check that as well.
 
Don’t assume the plug wire are good, verify with a resistance check (and check the plugs center electrode resistance as well).

Lightspeed ignitions, for whatever reason, eat plug wires. I guess that is way Klaus tells you to periodically replace them. I worked one RV-8 - four of twelve plug wires were bad and two of twelve plugs were bad (high resistance). Replaced wires and plugs, set the timing and the engine ran like a race horse.

Plug wire can also go bad from abrasion, heat and such.

High resistance plugs and plug wires play havoc on ignition coils (eMag or Lightspeed). Check them at every Condition Inspection).

Do all that, verify timing, then see what you have.

Carl
 
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And don't assume new plugs are good out of the box. It's rare, but I've seen some bad. A good visual inspection, gap and ohm check at every installation can save a bunch of troubleshooting down the road.
 
As stated test it for resistance. The resistance between the terminal and the metal base (ground) should be low. (Google it or youtube has lots of instructions on how to do this.)

If the resistance is infinity (no conductivity, open) plug is bad.

If it reads for example 5,000 ohm (5K ohm) it is likely a resistor plug. Check your EI manual for proper plug Part Number. Check your old plugs and see what their resistance is. Some ignitions have different specs, some require resistor plugs others without resistor.

This is only a basic test. Some plugs might have low resistance but act different under load. There are spark plug test machines that test the plugs under load (under pressure).

Counterfeit.... THERE ARE A TON OF FAKE NG's out there... Just go on eBay you will see them. There are some ways to tell but the fakes are getting better. They are not the same quality as the genuine.
 
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